Dietary effects on the reproductive performance of the sea urchin Tripneustes gratilla ll: Implications for offspring performance

Aquaculture practices can result in declines in the genetic diversity observed in progenitor natural populations, resulting in subsequent poor production output, particularly for broadcast spawning animals that frequently display differential parental contributions. This study aimed to assess the effect of different Tripneustes gratilla broodstock feeding regimes [formulated feed, kelp (Ecklonia maxima), green seaweed (Ulva lacinulata) and mixture of the three diets for four months] on larval growth, parental contributions and juvenile performance after a factorial breeding design was implemented. Larvae produced from broodstock fed kelp and the mixed diet survived for the full duration of larval rearing and displayed similar growth rates throughout (p > 0.05). Though larvae from Ulva-fed broodstock did not survive for the full duration of larval rearing, this could have been a consequence of larval rearing practices, as these larvae displayed a rapid increase in post-oral arm lengths prior to the mortality event. Furthermore, these larvae survived for the longest amount of time when left unfed, suggesting that the maternal reserves from animals fed Ulva as a broodstock conditioning diet could be beneficial to development in early larval stages. In contrast, larvae from animals fed a formulated feed did not survive the full duration of larval rearing and had developmental abnormalities. Three months post-metamorphosis, 10 species-specific microsatellite markers were PCR amplified across 16 broodstock and 364 offspring from kelp and mixed diet fed animals. Genetic diversity analyses showed that there were no statistically significant (p > 0.05) differences between the broodstock animals and their offspring, showing that factorial breeding designs are advantageous to preserve genetic diversity present in cultured cohorts. Parentage analyses revealed that a total of 26 out of 32 possible F1 parent pairs contributed to the F2 generation, with a low heritability estimate of approximately zero (0.050 ± 0.058) for offspring body diameter, likely as offspring phenotypic performance is not influenced by additive genetic effects during these early growth stages.